The present invention relates to the field of sound direction detection.
The need to detect the exact direction of arrival (DOA) of a sound is highly important in a variety of fields. Detecting the direction of the sound emitted by a shooting firearm, for instance, might be crucial both for military and civic situations. Due to the changing nature of armed conflicts and the increase in attacks by guerillas, armed civil conflicts, and of humanitarian action given in unstable regions, receiving accurate and reliable data about the position of a shooter may allow damage reduction by enabling the appropriate responses. U.S. Pat. No. 5,586,086 provides a means for locating a firearm on the basis of acoustic detection. The disclosed method and system detect the location of a firearm firing projectiles by using an acoustic detection antenna that includes at least three microphones spaced apart from one another to detect and record signals and time offsets of the signals which are representative of the muzzle noise of the firearm and/or the sound wave emitted by the mach cone generated by a projectile that has supersonic muzzle velocity, and processing the signals and their time offsets in such a manner as to determine at least the direction in which the firearm is located.
U.S. Pat. No. 6,185,153 is a system for detecting gunshots, which includes an input device including a microphone for converting acoustic noises into signals and amplifiers for amplifying the input signals, a threshold detector for receiving the amplified signals and comparing the signals with a predetermined threshold value and for producing an output signal when the threshold value is exceeded. A pulse width detector is connected to the threshold detector for producing an output signal only if the width of the threshold detector output signal is within a predetermined range of values. A pulse count detector is also connected to the threshold detector for producing an output signal when the level of the threshold output signal is above a peak threshold level or the number of threshold level output signals that exceed a threshold level are less than a preset limit. An output device indicates that a gunshot has occurred only when signals are received from the pulse width detector and the pulse count detector during a sampling period.
Another field in which sound direction detection is important is in the field of security systems which include surveillance cameras. The limited angle of view of security cameras often dictates making use of several cameras in order to provide a full visual coverage of a given area. This solution increases the complexity and cost of such systems. One traditional means for overcoming this problem includes regularly rotating the direction of the camera, but this solution might cause the camera to be directed in the wrong direction in critical moments. The integration of a sound direction detection system into such systems helps overcome this limitation and to make them more efficient and reliable.
Security systems that do implement such methods integrate other methods of directional detection as described in U.S. Pat. No. 4,857,912. This system utilizes multiple sensors for detecting intrusion into an area. Each of the sensors operates on a different principle to detect intrusion. Sound, vibration, infra-red, motion detection, microwave and light level sensors are used, for example, which obviously makes it a highly complex and costly solution.
There is therefore a need for a simple and highly reliable system and method for detecting the direction of an emitted sound which can be adjusted to suit the different needs of different systems. The solution should also be able to supersonic as well as sonic sounds and be compact and lightweight enough to be carried by a person.